I believe Ayn Rand admired Cooper more for his conformity to the physical ideal of masculinity than for his acting. Personally, I think he was a poor actor, the Kevin Costner of his era. Sadly, this movie simply could not be The Fountainhead with him at the helm.
With all due respect to those who have stated otherwise, I also believe that the actor who portrayed Toohey really didn't "get it." In the novel, Toohey is so dangerous because of his misapplication of great insight and intellect (driven by his bankrupt core values). The actor in the movie to my view played him more as a straight heel, oblivious to the nature of a true Toohey - a serious misrepresentation.
Lastly, I just don't think the novel could translate well into a Hollywood-friendly length film, although I admire the ambition to accomplish this. I rented this movie maybe 15 years ago to show to a group of friends, knowing that Rand thought it a proper reflection of her work and hoping to introduce them to Objectivism through it. Unfortunately, it just left them scratching their heads. They simply found it to be a mediocre movie, as (regretably) did I. The gap between what I wanted to think and what I actually saw was unbridgeable; the reaction of 3 intelligent friends showed me that the film didn't adequately transcend its limitations to communicate the Objectivist world view.
Again, I am not trying to be disrespectful. I know I am new here and am not simply trying to make waves; I was sincerely disappointed by the movie, though, and could not recommend it.